This invention relates in general to luminous displays and in particular to a luminous display employing a gas discharge and a method of manufacturing such a display.
Luminous flat glass signs employing a gaseous discharge and methods for making such signs have been disclosed in several patents. In general, these flat glass signs are made by using two or three glass plates with a groove or cavity corresponding to the desired display formed in one or two of the plates. When three plates are used, the groove or cavity can be formed in the intermediate plate which is disposed between a pair of outer plates. Alternately, the intermediate plate can be omitted with the groove or cavity formed in an interior surface of one or both of the outer plates.
Referring now to the drawings, where like reference characters represent like elements, there is illustrated in FIG. 1, a typical prior art luminous gas discharge display 10. The luminous gas discharge display 10 includes a front plate 12 which is opposite to a back plate 14. The front and back plates 12 and 14 may be formed of most any suitable thickness and size to withstand temperatures and vacuum levels of gas discharge. At least the front plate 12 is formed of a transparent material such as glass or plastic or the like.
At least one of the plates 12 and 14 includes a channel 16 formed in an interior surface thereof. The channel 16 defines a gas discharge path and may be of most any suitable configuration or length. The channel 16 may be in the shape of a continuous tortuous path or in the shape of multiple independent paths configured to appear as a reference character such as letters or numbers. For illustrative purposes, the channel 16 is shown in FIG. 1 in the shape of the Greek letter xe2x80x9cxcexa9xe2x80x9d. A sealing layer 17 is disposed between the plated 12 and 14 and forms a hermetic seal therebetween.
The display 10 further includes at least two electrodes 18 and 19 that are in direct contact with the gas within the channel 16. The electrodes 18 and 19 are of a conventional design and energize an ionizable gas which is contained within the channel 16. As illustrated in FIGS. 1, the electrodes 18 and 19 are located between the plates 12 and 14. Electricity to power the display 10 is supplied to the electrodes 18 and 19 by a transformer (not shown) through lead wires 20 and 21 as is well known in the art.
The channel 16 is filled with an ionizable gas, such as, for example, mercury, xenon, krypton, neon or argon, or mixtures of ionizable gases. A charging port 24, which comprises a glass tube extending through the back panel 14, communicates with the channel 16. After the display panel 10 has been assembled, any gases within the channel 16 are evacuated through the charging port 24 and then the channel 16 is refilled with a selected ionizable gas or mixture of such gases. Typically, the charging port 24 can be sealed by a xe2x80x9ctip offxe2x80x9d operation during which the glass tube is heated and stretched to pinch and separate the tube and thus form a seal. While the charging port 24 is illustrated as extending through the back plate 14, it also be appreciated that the invention can be practiced with the charging port 24 extending through the front plate 12 or an edge of the display 10.
To further enhance the display 10, a light emitting phosphor (not shown) can be applied to the interior surface of the front plate 12, to the interior surface of the back plate 14, or to the interior surface of the channel 16. When the display 10 includes a light emitting phosphor, a small amount of liquid mercury (Hg) is included in the channel. The natural vapor pressure of the Hg fills the channel 16 with Hg in its gaseous state. The resulting Hg vapor emits UV radiation when excited by the electrical discharge through the channel 16. The UV radiation excites the phosphor, causing the phosphor to emit a colored light. The color of the emitted light is determined by the particular phosphor utilized. The phosphor changes the light color of the display 10 as required to improve the aesthetics of the display.
During operation of the display 10, a longitudinal gas discharge is established between the electrodes 18 and 19 to form a long positive column discharge. Because of the length of the channel 16 a relatively high voltage, typically within the range of six to nine kilovolts, is required to be applied to the electrodes 18 and 19. Additionally, the mercury vapor within the channel 16 can be hazardous if accidentally released from the channel 16. Prior to the development of flat glass signs, illuminated displays typically used fragile glass tubes that were filled with a mixture of neon gas and mercury vapor. Accordingly, it would be desirable to provide a display that uses a lower electrode voltage and does not require Hg. Additionally, it also would be useful to increase the operating efficiency of the display.
This invention relates to a luminous display employing a gas discharge and a method of manufacturing such a display.
The present invention contemplates a light display that includes a first plate and a second plate, each of which has an interior surface and an exterior surface. The first plate is attached to the second plate by a seal with the interior surfaces of the plates facing one another. A cavity is disposed between the plates and a layer of phosphor is deposited upon an interior surface of one of the plates. A least one electrode in formed upon an exterior surface of one of the plates and a second electrode is formed upon a surface of the other of the plates. The cavity is filled with a gas mixture.
The invention further contemplates that the second electrode can be formed upon either an exterior or an interior surface of the other plate. Additionally, the gas mixture includes noble gases while excluding mercury.
Upon application of an alternating voltage to the electrodes, the gases within the channel break down and emit ultraviolet light. The ultraviolet light excites the atoms in the phosphor, causing the phosphor to emit a visible light in a color that is a characteristic of the particular phosphor.
The invention also contemplates a method for making a light display that includes the steps of providing a first plate and forming a continuous channel in a surface of the first plate. A phosphor is deposited within the channel and a second plate is attached to the first plate with the channel located between the first and second plates. A first surface electrode is applied to an exterior surface of the first plate and a second surface electrode is applied to an exterior surface of the second plate. The channel is then evacuated and subsequently charged with a mixture of noble gases.
Various objects and advantages of this invention will become apparent to those skilled in the art from the following detailed description of the preferred embodiment, when read in light of the accompanying drawings.